Originally Posted by
grizzly59
I've had a Gitane. Great bike. French bikes can be very confusing as to part dimensions. I think makers like Gitane have had different sizes for parts depending on where they were expected to be sold. But even then who knows. I wouldn't speculate with anything French, I would use a caliper and do an admiral Hopper and measure for a real answer on a particular bike.
And like Trailangel said, try and clean / service / adjust the one you've got now.
https://www.sheldonbrown.com/cribsheet-headsets.html
+1...the frame tubing diameters on most of the French stuff from that era are unique, so it can be troublesome to find a replacement that will work. In addition, a lot of the older French cycles had a different standard for the crown race diameter, so if you can make the old one work, even if you need to shim the head races with some aluminum can stock, you're usually better off. The threading on the fork is different, you need to worry about stack height in a newer one.........all in all, I go to great lengths to make the original work on these.